Electrically heated wall for a spray fog testing chamber



mi. J

Oct 25, 1950 R. 1 sElDMAN 2,957,972

ELECTRICALLY HEATED WALL FOR A SPRAY FOG TESTING CHAMBER Filed Oct. 28, 1958 COLD WATER United States Patent O ELECTRICLLY HEATED WALL FOR A SPRAY FOG TESTING CHAMBER Richard L. Seidman, 9 1Cross St., Norwalk, Conn.

Filed Oct. 28, 1958, Ser. No. 770,059

3 Claims. (Cl. 219-19) This invention relates generally to the field of environmental test equipment, and more particularly to an improved salt spray fog test chamber, or similar device in which the deleterious effect of salt spray fog or of simple humidity or fungus may be determined by simulating conditions in which materials will be used in actual use.

The procedure in salt spray fog testing has been standardized in recent years, the critical conditions and requirements being fully set forth, for example, in a pamphlet published by the American Society for Testing Materials, of 1916 Race Street in Philadelphia 3, Pa., entitled Tentative Method of Salt Spray (Fog Testing) Among the principal requirements are provision for the supplying of a continuous fog of vaporized salt solution, provision for preventing drops of solution which accumulate on the ceiling or cover of a chamber from falling upon the specimens being tested, provision for prevention of re-use of contaminated solution, and provision of materials comprising the testing chamber such that the corrosiveness of the fog shall not be affected.

During the period of test, the chamber must be maintained within relatively narrow limits at a point above normal room temperature, the pH factor and specific gravity of the solution must also be maintained within limits.

In maintaining the temperature at the required level, the method of heating of the chamber must be external to comply with specified testing procedures. In the past, this heating has been accomplished by strip electric heaters which are clamped to the underside of the bottom or sides of the chamber. This method has resulted in an extremely wide variation of temperature within the chamber. Another solution has been the use of waterjacketed walls. This is a relatively good system, but suffers from undue complication in the necessity of providing auxiliary equipment such as a water circulator, a float valve, water and drain connections, etc.

Therefore, it is among the principal objects of the present invention to provide an improved heating system which will achieve an effect comparable to that achieved with water-jacketed walls, but without the accompanying complication present in the prior art method.

Another object of the invention lies in the provision of an improved fog test chamber of the class described in which the cost of manufacture may be of a reasonably low order, with consequent Wide sale, distribution and use.

A feature of the invention lies in the provision of an improved bubbling tower for humidifying the air entering the test chamber, in which means is incorporated for preventing the flow of water back and into the source of compressed air.

These objects and features, as well as other incidental ends and advantages, will more fully appear in the course of the following disclosure, and be pointed out in the appended claims.

On the drawing, to which reference Will be made in the specification, similar reference characters have been employed to designate corresponding parts throughout the several views.

Figure 1 is a view in perspective showing an embodiment of the invention.

Figure 2 is a side elevational view, partly broken away to show internal detail.

Figure 3 is a fragmentary enlarged sectional view showing the details of an individual spraying nozzle which comprises a part of the device.

Figure 4 is a schematic piping diagram.

Figure 5 is an enlarged vertical fragmentary sectional view showing details of construction of the side and top walls of the embodiment.

In accordance with the invention, the device, generally indicated by reference character 10, comprises broadly: a ioor element 11, a plurality of side wall elements 12, 13, 14 and 15, a roof or lid element 16, pivotal means 17 including a pair of hydraulic cylinders 18 and 19 for opening said lid element, and side door means 21. The above elements are arranged to form an enclosed chamber, as is well known in the art, the interior of which supports one or more spray nozzles 22 which, in operation, form a continuous fog which is allowed to Contact the exposed surface of the articles being tested.

Referring to Figure 3 on the drawing, the individual spray nozzles 22 are substantially similar, each including a salt solution inlet 23, a pressurized air inlet 24 and a fog outlet 25 as well as regulating means 26.

Referring to Figure 4, a salt water reservoir 29 is periodically lled with a proper solution, and is fed by gravity suction or pressure to the nozzles 22. Drain valve means 3th communicates with a drain pipe 31, permitting the solution contained within the reservoir 29 to be replaced with fresh solution as needed. The feed line 32 communicates with the inlet 23 described above. A source of compressed air, generally indicated by reference character 34 is fed through a strainer 35 and pressure regulator 36 to a check valve 37 by way of a looped portion 3S, the highest portion of which extends above the level 40 of water 41 in a bubble tower 39. Float valve means 42 maintains the level 40 at a relatively constant value, while a drain valve 44 permits emptying of the bubble -tower as needed. A water inlet valve 45 supplies Water to the oat valve 42.

Compressed air emanating from the source 34 is passed through the water 41 in the bubble tower 39 to permit the same to be humidified prior to passing air pressure and temperature gauges 46 and 47, respectively, on its way to the air inlet 24 of the individual nozzles 22.

By employing the connections shown, Water passing through the valve 45 may be conducted through lines 49 to operate the cylinders 18 and 19 to raise or lower the lid lement `16 with respect to the side wall elements 12- 6.

Referring to Figure 5, there is shown the laminar relation of the parts comprising the wall and lid elements 12-16 inclusive. The outer shell 53 may be formed of sheet synthetic resinous material or sheet metallic material, as desired. It may be of relatively thin gauge, consistent with mechanical strength necessary for selfsupport. A relatively thick insulative lining 54, preferably of berglass or similar material contacts the inner surface of the external shell 53, the inner surface of the lining 54 in turn `being covered by an electrically conductive rubber blanket 55. Means (not shown) is provided for the passage of an electric current through the blanket whereby the same performs a heating function. The blanket 55 consists essentially of a rubber pad made of conductive rubber, the size being substantially equal to the area of the wall elements and/or lid elements so that a very even heat output per square foot of area is obtained. Rubber pads of this type are currently manufactured in this country by the United States Rubber Company, UsKon Division, Akron, Ohio.

The inner layer of the blanket 55 is coated With an adhesive layer 56 upon which, in turn, a lining 57 of non-corrosive steel iis*` placed. -Where cost.isafactor, a layer of conventional steel may be used,provided'a second protective'layer (notshown) o-iin'ert synthetic resinous material is employed as a iinal liner. Such materials as polyvinylchlorideprovide'a glossy surface which is simple to clean, and the material can easilyabe repaired in position,- `shouldthe same become-cut or torn. Thermostats one of which is indicated by reference character 59 are preferably placed directly in the adhesive-layer 56, it being possible for a` single thermostat to control a relativelywide area, including more than one panel.

By utilizing the above construction vin theY lid element as well as the side wall elements, substantially all of the interior surface of the chamber (oor excepted), the condensation Yof moisture upon the interior surface, particularly the lid element,is reduced, thereby lessening the likelihood offdropl'ets of salt solution falling upon the specimens being tested, a condition not permitted under generally accepted practice.

As the above described construction permits a substantially uniform temperature to be maintainedthroughout the chamber, sensing thermostats may be placed at any desired position Within the chamber without' fear of substantial temperature variation.

It may thusbe seen -that I have invented novel and highly useful improvement in `salt spray fog test chambers and similar devices, in which all of the requirements required by standard practice havebeen fullled While maintaining the cost of manufacture of the device Within reasonable limits. yBy the use of simple radiant heating means, a temperature uniformity is obtained comparable With that obtained in the prior art only by a use of water-jacketedwalls, a far more expensive construction not suitable for use inwall segments which are moved to provide an opening into the chamber, such as lid elements, door elements, and the like. Use is made of available Water pressure not only to supply a means for humidifying compressed air, but also for operating hydraulic cylinders which openV and close the device as Well. By providing a check valve in the compressed air line in conjunction with a portion of the ycompressed air line which extends to a point above the Water level of the bubble tower employed' for humidifying the compressed air, lthe possibility of Water being fed back into the compressed `air line is substantially eliminated With a minimum of complication.

I wish it to be -understood that IA do not consider the invention limited to the precise details of structure shown and set forth in this speciticatiomfor obvious modications will occur to those skilledin the art to which the invention relates.

I claim:

1. Wall in a structure for use in conjunction with :an electrically heatedsalt spray fog testing chamber including an outer shell of relatively rigidV material, a layer of heat insulative materials disposed upon the inner surface of said outer shell, `a blanket of kelectrically conductive rubber disposed upon said layer of heat insulative ma terial, and a layer of lining material disposed upon said blanket, the same being. chemically inert to salt spray.

2. Structure according to claim l in Which said last mentioned material is polyvinyl chloride.

3. Structure according to claim 1 in which said last mentioned material is non-corrosive steel.

References Cited in the le of this patent UNITED STATES PATENTS 2,386,095 `Edgar et al. Oct. 2, 1945 2,505,117 Homann Apr. 25, 1950 2,613,306 Waltersdorf et al. Oct. 7, 1952 2,683,673 Silversher July 13, 1954 2,799,764 Chandler July 16,1957 2,873,352 Franco Feb. 10, 1959 

